Hierarchical broadcast transmission via multiple transmitters

ABSTRACT

A technique for controlling a wireless broadcast transmission of media data via multiple transmitter sites into a broadcast area with different inter-site distances is proposed. The broadcast area comprises a region of large inter-site distance (ISD) and a region of small inter-site distance. The technique provides for a high spectral efficiency in regions of small ISD and at the same time for an acceptable reception quality in regions of large ISD. A first transmission is initiated into the broadcast area, wherein the first transmission is adapted for reception in a first of the regions. A second transmission is initiated into a second of the regions, the second transmission being adapted for reception in the second region.

FIELD OF THE INVENTION

The invention relates generally to the field of wireless broadcasttransmissions of media data. More specifically, the invention relates toa technique for controlling a wireless broadcast transmission of mediadata via multiple transmitter sites into a broadcast area with differentinter-site distances.

BACKGROUND OF THE INVENTION

Broadcasting services provide for the transmission of media data, forexample streaming audio and/or video data, from typically a single datasource to multiple receivers. Modern broadcasting services often makeuse of a wireless technology to transmit the media data over at least anessential segment of the way from the data source to the receivers.Wireless broadcasting services may not only be provided by classicalradio stations and television networks, but also by mobile networks, forexample GSM (Global System for Mobile Communications) or UMTS (UniversalMobile Telecommunications System) networks.

Each broadcasting service is provided into a broadcast area, i.e. into ageographical area in which the media data can be received. In case of aPLMN (Public Land Mobile Network), the broadcast area may comprise thewhole network. On the other hand, a broadcast area may be configured tobe as small as a single radio cell of a cellular network. In general, abroadcast service area comprises a reasonable part of a PLMN.

Each network cell is served by a transmitter site comprising at leastone transmitter or transmitter station. For example, a transmitter sitein a GSM network comprises a BTS (Base Transceiver Station) which may becontrolled by a BSC (Base Station Controller); a transmitter site in aUMTS network comprises a Node-B which may be controlled by an RNC (RadioNetwork Controller). Consequently, multiple transmitter sites arerequired at least for broadcast areas comprising many cells. Themultiple transmitter sites may use the same frequency resource, i.e.operate on the same frequency; this operational mode is called SingleFrequency Network (SFN).

To minimize interference, the transmitter sites of an SFN are typicallyrun synchronised with each other, i.e. all transmitters of the multiplesites synchronously transmit the same broadcast signal. This may beachieved for example by using GPS (Global Positioning System) or areference clock provided by one of the transmitter sites or by a controlnode in the broadcast network. A receiver, e.g. a receiver component ina user equipment of the mobile network, thus receives broadcast signalsof multiple nearby transmitter sites.

The receiver may superpose the signals received from transmitter siteswithin a certain distance from the receiver. Signals received from moredistant transmitter sites contribute to the interference level at thelocation of the receiver. As an example, an OFDM (Orthogonal FrequencyDivision Multiplex) broadcast system uses a particular guard intervalthe length of which determines the maximum distance for constructivesuperposition. Examples of OFDM-based broadcast systems are DVB-T(Digital Video Broadcasting-Terrestrial) and DAB (Digital AudioBroadcasting).

To achieve at the same time a predetermined minimum reception quality interms of a maximum bit or packet error rate over the entire broadcastarea and a high spectral efficiency (ratio of media data bit rate torequired transmission bandwidth), an important measure is provided bythe Signal to Interference plus Noise Ratio (SINR). The lower the SINR,the higher the error rate. In order to achieve a desired error rate andbit rate for a low SINR, a transmission mode is required which utilizesmore radio resources than a transmission mode adequate for a high SINR,thus decreasing the spectral efficiency.

The transmission mode determines the coverage of the transmission, i.e.the zone around a transmission site wherein reception of the transmittedbroadcast signal is possible for a receiver with a bit or packet errorrate below a predetermined quality threshold. In cellular networks,radio resources may for example be specified according to one or more ofthe aspects time, frequency, transmit power and spreading code.Accordingly, the transmission mode is specified by choosing for examplea particular transmit power, a particular channel coding (e.g., higheror lower code rates), particular spreading codes with specific spreadingfactors, etc.

By its definition, the SINR at a receiver at a particular location inthe broadcast area increases with the received aggregate useful signal,which is the superposition of all useful signals from individualtransmitters, and decreases with the aggregate interference, which isthe superposition of all interfering signals from individualtransmitters, and with the noise level, which may be assumed to be alocation independent constant. Depending on the deployment of thebroadcast network, either the interference can dominate the noise orvice versa. If the noise dominates, the SINR increases with decreasingdistance to the transmitters. Even if the interference dominates,generally the SINR increases with decreasing distance to thetransmitters, because the interference will increase less than theuseful signal.

Accordingly, the minimum SINR in an SFN broadcast area is generallydependent on the inter-site distance (ISD), defined as the averagedistance between any pair of transmitter sites in a region of thebroadcast area. The SINR typically decreases with increasing ISD. Theminimum SINR in a broadcast area typically occurs in a region of thebroadcast area with a large ISD.

The minimum SINR (which may be a percentile) in a given broadcast areais generally determined by measurement. Then a transmission mode ischosen to achieve the desired error rate. However, in an SFN network,increasing for example the transmit power might be sufficient toincrease the Signal to Noise Ratio, but at the same time may increaseinterference and thus lead to a decreasing SINR. The minimum SINR in thebroadcast area may also decrease (and may occur at different locationsin the broadcast area).

Using different transmission modes on the same radio resources wouldmake it more difficult to superpose the signals received fromtransmitter sites using the different modes, in particular in the caseof SFNs. In SFN broadcast areas comprising a region or regions of smallISD (e.g., cities) and a region or regions of large ISD (e.g., ruralareas), it is thus difficult to find an optimal transmission mode. Incase a transmission mode is chosen which is sufficiently robust toachieve full coverage also in the region of large ISD, this transmissionmode will not exploit the higher SINR achieved in regions of small ISDand therefore the spectral efficiency in these regions will be lowerthan in the case that a less robust transmission mode had been used thatstill achieves full coverage in regions of small ISD.

In regions of small ISD the SINR is high. This allows to achieve fullcoverage even for transmission modes which are less robust and cantherefore provide a higher throughput. These transmission modes arehowever not sufficiently robust for the regions of large ISD andtherefore cannot achieve full coverage in these regions.

Accordingly, there is a need for a technique for controlling a wirelessbroadcast transmission of media data via multiple transmitter sites intoa broadcast area with different inter-site distances, wherein thetechnique provides for a high spectral efficiency in regions of smallISD and at the same time for an acceptable reception quality in regionsof large ISD.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, a method of controlling awireless broadcast transmission of media data via multiple transmittersites into a broadcast area with different inter-site distances isproposed, wherein the broadcast area comprises at least a region oflarge inter-site distance and a region of small inter-site distance, andwherein the method comprises the steps of initiating a firsttransmission into the broadcast area, the first transmission beingadapted for reception in a first of the regions; and initiating a secondtransmission into a second of the regions, the second transmission beingadapted for reception in the second region.

The regions of large inter-site distance and of small inter-sitedistance may be determined or defined in various ways, e.g. by anoperator of a network comprising the broadcast area. Alternatively,transmitter sites may also determine their membership to a particular ofthe regions by detecting distances to their neighbouring sites. In casethe detected distances fall on the average below a predeterminedthreshold value, the transmitter site determines itself to be in theregion of small ISD, and in case the detected distances are on theaverage above the threshold value, the site falls into the region oflarge ISD. The threshold value may for example be dependent onatmospheric conditions or other parameters.

More than just two regions of different ISD may be defined; for example,three regions of large, intermediate and small inter-site distance maybe defined, e.g. by defining intervals with respective upper and lowerthresholds, with transmissions being specifically adapted for receptionin any of these regions.

The adaptation to the regions of small and large inter-site distance,respectively, may comprise adjusting the transmission mode such that apredetermined bit or packet error rate will be achieved at a receiverlocated in the region. The transmission mode specifies at least thecharacteristics of radio resources utilized for transmitting thebroadcast signal representing the media data. The transmission mode mayfor example specify the usage of time slots, frequency channels,transmit power and/or spreading codes.

The first transmission may be adapted for reception in the region oflarge inter-site distance and the second transmission may beaccomplished into the region of small inter-site distance, the secondtransmission then being adapted for reception in the region of smallinter-site distance. The first transmission may be used to provide abasic quality to the entire broadcast area, whereas the secondtransmission provides an enhanced quality to the region of smallinter-site distance.

As an example, the media data may comprise hierarchically layered datawith at least a base layer and an enhancement layer. The base layerprovides a basic media presentation quality, and the enhancement layeradds further quality. The step of initiating the first transmission maythen comprise initiating a transmission of the base layer and the stepof initiating the second transmission may comprise initiating atransmission of the enhancement layer.

The method aspect of the invention discussed here may comprise thefurther steps of determining if transmission resources for atransmission of the enhancement layer are available at one or moretransmitter sites of the region of large inter-site distance. In case ofavailable transmission resources, a third transmission may be initiatedvia the one or more transmitter sites into the region of largeinter-site distance. The third transmission may be adapted for receptionof the enhancement layer in the region of large inter-site distance.

The available transmission resources for the third transmission maycomprise resources usually used for unicast transmissions performed bythe same transmitter sites. For example, in a mobile network, unicastand broadcast transmissions can be performed using the same antennas. Inmodern cellular networks it is possible to split the radio resources ata transmitter site as required for broadcast and unicast traffic, i.e.the splitting may be adjusted according to demand.

Although performed into the region of large ISD, the third transmissionmay alternatively also be adapted for reception in the region of smallISD. In this case the third transmission may extend the secondtransmission, which concerns the transmission of the enhancement layerinto the region of small ISD, and being adapted to the region of smallISD, into the region of large ISD, but without adaptation to the regionof large ISD. At least receivers nearby to a transmitter site in theregion of large ISD will receive the enhancement layer. No additionalradio transmission resources are required in this case of hierarchicalmodulation, in which the base layers and the enhancement layers aretransmitted via the same radio transmission resource.

In the case, that the third transmission is adapted for reception in theregion of large ISD, the enhancement layer is broadcasted into theentire service area at the expense of additional radio resources used inthe region of large ISD (as compared to the transmission into the regionof small ISD).

The second transmission may comprise transmitting a singlerepresentation of the media data and the third transmission may comprisetransmitting multiple representations of the media data, in this wayadapting the transmissions of the enhancement layer for to the region ofsmall and large ISD, respectively.

Alternatively, the first method aspect discussed here may comprise thefurther steps of transmitting a subset of the media data of theenhancement layer via the second transmission, and transmitting themedia data of the enhancement layer via the third transmission. Forexample, the method may comprise the steps of indicating in a bit streamassociated with the media data of the enhancement layer bits that may beomitted in a transmission, transmitting the bit stream via the secondtransmission excluding the omitted bits and transmitting the bit streamvia the third transmission including the omitted bits.

For instance, a common channel coding may be initiated for the mediadata of the enhancement layer for the second and the third transmission.Further, a puncturing of an encoded bit stream resulting from the commonchannel coding may be initiated. Then in the second transmission onlythe encoded bitstream excluding the punctured bits is transmitted intothe region of small ISD, whereas in the third transmission the encodedbit stream including the punctured bits is transmitted into the regionof large ISD. The third transmission may include the complete bitstreamor only the punctured bits.

The transmitter sites of the broadcast area may perform the firsttransmission each utilizing one and the same frequency and/or timeresource and may perform the further transmission(s) utilizing differentfrequency and/or time resources. For example, the transmission of thebase layer may be performed according to the principles of an SFN, andthe second transmission may be performed at different times or ondifferent frequencies at neighbouring sites.

The method aspect of the invention discussed here may comprise that thefirst transmission (into the entire broadcast area) is adapted forreception in the region of small inter-site distance and the secondtransmission is accomplished into the region of large inter-sitedistance, the second transmission being adapted for reception in theregion of large inter-site distance. Thus, the first transmission maynot fully cover the region of large inter-site distance.

One and the same broadcast signal representing the media data may betransmitted in the first transmission and in the second transmission.The transmissions may however utilize different transmission resources,such that the second transmission into the region of large ISD utilizesmore or additional transmission resources than the first transmission(i.e. compared to the resources utilized by the first transmission) forproviding the media data with an acceptable quality into the region oflarge ISD.

As an example, the first transmission may comprise transmitting a singlerepresentation of the media data and the second transmission maycomprise transmitting multiple representations of the media data. Forinstance, multiple copies of OFDM symbols may be transmitted in thesecond transmission using additional transmission resources, namelyadditional time slots and/or frequency (sub)channels.

As another example, the method may comprise the further steps oftransmitting a subset of the media data of the enhancement layer via thefirst transmission, and transmitting the media data of the enhancementlayer via the second transmission. The method may e.g. comprise thesteps of indicating in a bit stream associated with the media data ofthe enhancement layer bits that may be omitted in a transmission,transmitting the bit stream via the first transmission excluding theomitted bits and transmitting the bit stream via the second transmissionincluding the omitted bits.

For instance, the method may comprise the step of initiating a commonchannel coding for the media data for the first and the secondtransmission. Then, in the first transmission only a subset of theencoded media data may be transmitted, namely the encoded bitstreamexcluding the punctured bits, and in the second transmission, theremaining bits of the encoded data are transmitted, namely the puncturedbits of the encoded bit stream. In the alternative, in the secondtransmission a bitstream including the punctured and the unpuncturedbits may be transmitted.

According to a second aspect of the invention, a method of controlling awireless broadcast transmission of media data via multiple transmittersites into a broadcast area with different inter-site distances isproposed, wherein the broadcast area comprises at least a region oflarge inter-site distance and a region of small inter-site distance, andwherein the method comprises the steps of initiating a firsttransmission into a cell served by a transmitter site, the firsttransmission being adapted for reception in the region of largeinter-site distance; and initiating a second transmission into the cell,the second transmission being adapted for reception in the region ofsmall inter-site distance.

The transmitter at the transmitter site thus performs at least twotransmissions. The transmitter may for example be located anywhere inthe broadcast area and may transmit in the first transmission a baselayer of hierarchically encoded media data and in the secondtransmission an enhancement layer. In another example, the transmittermay be located in the region of large inter-site distance and maytransmit in the first transmission a subset of the media data sufficientfor decoding the broadcast signal in the region of small ISD, and maytransmit in the second transmission at least a portion of the remainingbits. In general, the first (second) transmission according to thesecond method aspect of the invention may coincide with the first(second) transmission of the first method aspect of the inventiondiscussed further above, or may coincide with the second (first)transmission of the first method aspect of the invention.

According to a third aspect of the invention, a method of receiving awireless broadcast transmission of media data via multiple transmittersites into a broadcast area with different inter-site distances isproposed, wherein the broadcast area comprises at least a region oflarge inter-site distance and a region of small inter-site distance. Themethod comprises the steps of receiving a first transmission from atleast one transmitter site, the first transmission being adapted forreception in the region of large inter-site distance; and receiving asecond transmission from at least one transmitter site, the secondtransmission being adapted for reception in the region of smallinter-site distance.

The media data may for example comprise hierarchically layered data withat least a base layer and an enhancement layer. Then the firsttransmission may comprise a transmission of the base layer and thesecond transmission may comprise a transmission of the enhancementlayer. The transmissions may be received in the region of smallinter-site distance. They may also be received in the region of largeinter-site distance with acceptable reception quality close to atransmitter site.

Additionally or alternatively, one and the same broadcast signalrepresenting the media data may be transmitted in the first transmissionand in the second transmission, and the transmissions may utilizedifferent transmission resources. For example, after a common channelencoding, the first transmission may transmit an encoded bit streamomitting punctured bits, whereas in the second transmission thepunctured bits are transmitted.

According to another aspect of the invention, a computer program isproposed, the program comprising program code portions for performingthe steps of any one of the method aspects discussed herein when thecomputer program is run on one or more computing devices. The computerprogram may be stored on a computer readable recording medium.

According to still another aspect of the invention, a broadcast controlsystem for controlling a wireless broadcast transmission of media datavia multiple transmitter sites into a broadcast area with differentinter-site distances is proposed. The broadcast area comprises at leasta region of large inter-site distance and a region of small inter-sitedistance. The system comprises at least one first transmission controlcomponent adapted for initiating a first transmission into the broadcastarea, the first transmission being adapted for reception in a first ofthe regions; and at least one second transmission control componentadapted for initiating a second transmission into a second of theregions, the second transmission being adapted for reception in thesecond of the regions. This broadcast control system may implement thesteps of the first method aspect discussed further above.

One of the at least one first transmission control components may beadapted to initiate the first transmission which is adapted forreception in the region of large inter-site distance, and one of the atleast one second transmission control components may be adapted toinitiate the second transmission which is adapted for reception in theregion of small inter-site distance.

Additionally or alternatively, one of the at least one firsttransmission control components may be adapted to initiate the firsttransmission, which is adapted for reception in the region of smallinter-site distance and one of the at least one second transmissioncontrol components may be adapted to initiate the second transmissionwhich is adapted for reception in the region of large inter-sitedistance. Such a transmitter may therefore be utilized flexibly fordifferent transmission schemes within the framework of the invention.

The broadcast control system may further comprise a signalling componentfor initiating a transmission of control data related to the radioresources used for the first and second transmission into cells of thebroadcast area covered by both transmissions. For example, the systemmay use a signalling channel for transmitting information related to theframe numbers and identifiers of resource blocks in the transmittedframes, to allow the receiver to recombine the broadcasted data receivedin the first and the further transmissions to eventually recover themedia data.

According to a still further aspect of the invention, a transmitter forcontrolling a wireless broadcast transmission of media data into abroadcast area with different inter-site distances is proposed, whereinthe broadcast area comprises at least a region of large inter-sitedistance and a region of small inter-site distance, and wherein thetransmitter comprises a first transmission control component adapted forinitiating a first transmission into a cell of the broadcast area servedby the transmitter, the first transmission being adapted for receptionIn the region of large inter-site distance; and a second transmissioncontrol component adapted for initiating a second transmission into thecell, the second transmission being adapted for reception in the regionof small inter-site distance. This transmitter may implement the secondmethod aspect of the invention discussed further above.

According to another aspect of the invention, a radio access network(RAN) of a mobile network is proposed, comprising at least one of abroadcast control system and a transmission site as described herein.For example, it is possible to control a transmitter site or multipletransmitter sites by a control node in the RAN (or in a core network ofthe mobile network) to perform at least one of the first and secondtransmission. It is also possible to install control logic into some orall of the transmitter sites to enable them to autonomously decide onthe required transmission(s) and transmission mode(s).

According to a further aspect of the invention, a receiver component forreceiving a wireless broadcast transmission of media data via multipletransmitter sites into a broadcast area with different inter-sitedistances is provided, wherein the broadcast area comprises at least aregion of large inter-site distance and a region of small inter-sitedistance, and wherein the receiver comprises a first interface adaptedfor receiving a first transmission from at least one of the transmittersites, the first transmission being adapted for reception in the regionof large inter-site distance; and a second interface adapted forreceiving a second transmission from at least one of the transmittersites, the second transmission being adapted for reception in the regionof small inter-site distance. This receiver component may implement thesteps of the third method aspect of the invention discussed furtherabove.

According to a still further aspect of the invention, a user equipmentfor a mobile network is proposed, the user equipment comprising areceiver component according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will further be described with referenceto exemplary embodiments illustrated in the figures, in which:

FIG. 1 is a schematic illustration of an embodiment of a broadcast areacomprising multiple transmitter sites with different inter-sitedistances;

FIG. 2 is a schematic illustration of an embodiment of a radio accessnetwork (RAN);

FIG. 3A is a functional block diagram illustrating a first embodiment ofa broadcast control system implemented in an RNC;

FIG. 3B is a functional block diagram illustrating a second embodimentof a broadcast control system implemented in an RNC;

FIG. 3C is a functional block diagram illustrating an embodiment of abroadcast control system implemented in an RNC and Node-Bs;

FIG. 4 is a functional block diagram illustrating an embodiment of abroadcast control system implemented in a transmitter site;

FIG. 5 is a functional block diagram illustrating an embodiment of areceiver component implemented in a user equipment;

FIG. 6 is a flowchart illustrating a first method embodiment forcontrolling a wireless broadcast transmission of media data via multipletransmitter sites into a broadcast area with different inter-sitedistances;

FIG. 7 is a flowchart illustrating a second method embodiment forcontrolling a wireless broadcast transmission;

FIG. 8 is a flowchart illustrating a third method embodiment forcontrolling a wireless broadcast transmission;

FIG. 9 is a flowchart illustrating a fourth method embodiment forcontrolling a wireless broadcast transmission;

FIG. 10 is a flowchart illustrating a method embodiment for receiving awireless broadcast transmission of media data via multiple transmittersites into a broadcast area with different inter-site distances.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the following description, for purposes of explanation and notlimitation, specific details are set forth, such as specific networktopologies including particular network nodes, transmission modes, etc.,in order to provide a thorough understanding of the current invention.It will be apparent to one skilled in the art that the current inventionmay be practised in other embodiments that depart from these specificdetails. For example, the skilled artisan will appreciate that thecurrent invention may be practised with broadcast services differentfrom the GSM or UMTS broadcast services discussed below to illustratethe present invention. The invention may be practised in any networkenabled for wireless broadcast or, more generally, point-to-multipointtransmissions. For example, the invention may be applicable—besidesmobile networks—to (additionally or alternatively) WLAN, Bluetooth orsimilar wireless networks, and also to mobile or wireless networks whichmay be developed in the future.

Those skilled in the art will further appreciate that functionsexplained hereinbelow may be implemented using individual hardwarecircuitry, using software or firmware functioning in conjunction with aprogrammed microprocessor or a general purpose computer, using anapplication specific integrated circuit (ASIC) and/or using one or moredigital signal processors (DSPs). It will also be appreciated that whenthe current invention is described as a method, it may also be embodiedin a computer processor and a memory coupled to a processor, wherein thememory is encoded with one or more programs that perform the methodsdisclosed herein when executed by the processor.

The term ‘interface’ as used herein comprises ‘functional interfaces’. Afunctional interface designates a sub-structure contained within afunctional component or structure (a hardware, firmware and/or softwarecomponent or functional entity) intended for communication with other,external components or structures. A functional interface may be purelysoftware-implemented, for example if the structure, for which thefunctional interface provides the interfacing functionality, is asoftware component.

FIG. 1 schematically illustrates an embodiment 100 of a broadcast areacomprising multiple transmitter sites 102 for wireless broadcasttransmission of media data. The transmitter sites 102 may belong to aPLMN (not shown) and may in principle enable a complete coverage of thegeographical area given by the broadcast area 100 provided thatappropriate transmission modes are chosen.

The broadcast area 100 comprises a region 104, wherein the distancebetween neighbouring pairs of transmitter sites 102 (the inter-sitedistance ISD 106) is large, i.e. the ISD 106 is larger than apredetermined distance value, which may be configured by the operator ofthe transmitters 102. The threshold distance value may for example be ofthe order of one kilometer or several kilometers. The broadcast area 100further comprises a region 108, wherein the ISD is smaller than thethreshold distance value. The region of small ISD 108 may coincide forexample with a city or the central part of a city, whereas the region oflarge ISD 104 may coincide with a rural area. In other embodiments,instead of just two types of regions, several types of regions may bedefined, for example regions of small, intermediate and large ISD. Thebroadcast transmission of media data will be specifically adapted to theregions of different ISDs, as will be described in detail in thefollowing.

FIG. 2 illustrates an embodiment 200 of a radio access network (RAN) ofa mobile network 202. The network 202 further comprises a core network204. Media data for wireless broadcast transmissions are received fromthe core network 204 by a radio network controller (RNC) 206. The RNC206 controls Node-Bs 208 and 210, in the following also generallyreferred to as transmitter sites 208, 210. The transmitter sites 208,210 may be realizations of the transmitter sites 102 of FIG. 1. RNC 206may operate the transmitters 208, 210 in SFN-mode, i.e. the sites 208,210 synchronously transmit the media data into the broadcast area (notshown in FIG. 2). The broadcasted media data are received by a userequipment 212, which is located close to the transmitter sites 208, 210.

A broadcast control system for controlling a wireless broadcasttransmission of media data via multiple transmitter sites into abroadcast area with different inter-site distances may be implemented inthe RAN 200, namely in at least one of the RNC 206 and one or more ofthe transmitter sites 208, 210. The system may also be implemented in acontrol node (not shown) in the core network 204. Still further, thebroadcast control system may be distributed over nodes of the RAN 200and/or the core network 204.

FIG. 3A schematically illustrates an embodiment 300 of a broadcastcontrol system. The system 300 may be implemented in the RNC 206 of FIG.2, or may alternatively be implemented, for example, in a BSC of a GSMRAN. The system 300 receives media data via a splitting component 302.The data are forwarded to first, second, and third transmission controlcomponents 304, 306 and 308. After appropriate processing, the mediadata are forwarded to transmitter sites 310 and 312, which may beconstituted by the sites 208, 210 discussed above with reference to FIG.2.

Triggered by reception of the media data, the splitting component 302retrieves from a storage 314 information about the further components ofthe broadcast control system to which to forward the media data. The RNC300 controls the two transmitter sites 310, 312. Therefore, thecomponent 302 forwards the received media data to the three transmissioncontrol components 304, 306, 308 associated with the sites 310, 312. Thetransmission control components 304 to 308 may serve further transmittersites, and the RNC 300 may have further transmission control components,for example for further broadcast transmissions.

The splitting component 302 operates to split or separate a multi-layermedia data stream into one or more base layers and one or moreenhancement layers. The component 302 then forwards the base layer tothe transmission control component 304 and the enhancement layer to thetransmission control components 306 and 308.

The transmission control components further process the media data forpreparing first, second and third transmissions of the data via theassociated transmitter sites. It is assumed that transmitter sites 310and 312 are located in different regions of the broadcast area: The site310 is located in the region 108 of small ISD and the site 312 islocated in the region 104 of large ISD. The first control component 304operates to prepare the media data for the first transmission, i.e. theappropriate transmission mode for the first transmission. The firsttransmission is performed into the entire broadcast area, therefore thetransmission control component 304 forwards the processed data to bothtransmitter stations 310 and 312. The component 304 operates to preparethe base layer media data received from the splitting component 302 fora transmission adapted for reception in the region of large ISD.

The second transmission control component 306 operates to prepare themedia data for the second transmission, i.e. the appropriatetransmission mode for the second transmission. As the transmitterstation 310 is located in the region 108 of small ISD, the controlcomponent 306 prepares the enhancement layer media data for atransmission into the region 108 of small ISD (and adapted for receptionin the region of small ISD).

The third transmission control component 308 receives the sameenhancement layer media data from the splitting component 302 as thecomponent 306 and operates to prepare the forwarded enhancement layermedia data for a third transmission, which is performed into the regionof large ISD. The control component 308 processes the data received fromthe component 302 to prepare a transmission of the data specificallyadapted for reception in the region of large ISD.

In another embodiment, a puncturing component (not shown in FIG. 3A) maybe arranged between the splitting component 302 and the transmissioncontrol components 306, 308. Such a puncturing component may output abitstream omitting the punctured bits to the control component 306 forthe second transmission into the region of small ISD, and may furtheroutput a bitstream including the punctured bits to the control component308 for the third transmission into the region of large ISD.

FIG. 3B schematically illustrates another embodiment 320 of a broadcastcontrol system. The system 320 may also be implemented in the RNC 206 ofFIG. 2, or may alternatively be implemented, for example, in a BSC of aGSM RAN. The system 320 receives media data at an encoding component322. Encoded data are forwarded to a puncturing component 324, whichforwards the data to a first and a second transmission control component326 and 328. After appropriate processing, the media data are forwardedto transmitter sites 330 and 332, which may be constituted by the sites208, 210 discussed above with reference to FIG. 2.

The encoding component 322 performs a common channel coding of thereceived media data for both, the first and the second transmission. Thecomponent 322 then forwards the encoded data stream to the puncturingcomponent 324. The component 324 identifies bits (puncture bits) of thereceived bit stream, which may be omitted in the transmission into theregion of small ISD. The puncturing component then splits the bit streaminto a first bitstream, which does not contain the punctured bitsanymore, and a second bitstream, which does only contain the puncturedbits. The component 324 forwards the first stream to the firsttransmission control component 326 and the second bitstream to thesecond transmission control component 328.

The transmission control components 326, 328 further process thereceived bit streams for preparing a first and a second transmission viathe associated transmitter sites. It is assumed that transmitter sites330 and 332 are located in different regions of the broadcast area: Thesite 330 is located in the region 108 of small ISD and the site 332 islocated in the region 104 of large ISD. The first control component 326prepares the appropriate transmission mode for the first transmission,which is performed into the entire broadcast area. Therefore thetransmission control component 326 forwards the processed data to bothtransmitter stations 330 and 332.

The second transmission control component 328 receives the bit streamcontaining the punctured bits and prepares the appropriate transmissionmode for the second transmission into the region of large ISD, i.e. viathe transmitter site 332. The transmitter site 332 therefore transmitsthe first and the second bitstream.

FIG. 3C schematically illustrates an embodiment of a broadcast controlsystem which is implemented distributed over an RNC 340 and Node-Bs 342,344. The RNC 340 ma be an embodiment of the RNC 206 of FIG. 2, and theNode-Bs 342, 344 may be an embodiment of the Node-Bs 208, 210 of FIG. 2.The RNC 340 comprises two controller components 346 and 348 forcontrolling transmission of media data in the Node-Bs 342 and 344,respectively. The controller components 346, 348 may incorporate controlfunctionalities similar to the transmission control components of FIGS.3A, 3B.

The Node-B 342 comprises an encoding component 350, a puncturingcomponent 352, a modulator 354 and a power amplifier 356. The components350, 352, 354 and 356 in the Node-B 342 are controlled by the controllercomponent 346 of RNC 340 via signalling communications 357. The Node-B344 comprises an encoding component 358, a puncturing component 360, amodulator 362 and a power amplifier 364. The components 358, 360, 362and 364 in the Node-B 344 are controlled by the controller component 348of RNC 340 via signalling communications 365.

The media data to be transmitted comprise a single-layer data streamwhich is forwarded by the RNC 340 in data communications 366 and 367 viathe Iub interface known to the skilled person to the Node-Bs 342, 344.It is assumed that the Node-B 342 is located in a region of small ISD.The component 350 performs a channel encoding for the media datareceived from the RNC 340 and forwards the encoded data to thepuncturing component 352. The puncturing component punctures the encodedbit stream. A bit stream 368 comprising the punctured bits is not usedfor transmission, as illustrated in FIG. 3C by the loose end of thestream 368. A bit stream 370 comprising the unpunctured bits isforwarded to the modulator 354, which finally modulates the broadcastsignal, and the amplifier 356 for transmission of the unpunctured bitsonly into the region of small ISD.

The Node-B 344 is located in a region of large ISD. The component 358performs a channel encoding for the media data received from the RNC 340and forwards the encoded data to the puncturing component 352. Thepuncturing component punctures the encoded bit stream and forwards a bitstream 372 comprising the punctured bits and a bit stream 374 comprisingthe unpunctured bits to the modulator 362. The modulator 362 modulatesthe broadcast signal comprising the bitstreams 372 and 374 and forwardsthe signal to the amplifier 364 for transmission of both the puncturedand the unpunctured bits into the region of large ISD.

In other embodiments, the transmission control components (controllercomponents) or multiple implementations thereof may be implemented in anode of the core network. In still other embodiments, the preprocessingcomponents or controller components may also be located in a dedicatednetwork node.

FIG. 4 illustrates an embodiment 400 of a broadcast control systemimplemented in a transmitter site. The transmitter site 400 may be a BTSof a GSM-RAN or a Node-B of a UMTS-RAN. For example, the transmittersite 400 may be one of the sites 102 of FIG. 1 or one of the sites 208,210 of FIG. 2. In the following, it is exemplarily assumed that thetransmitter site 400 is an embodiment of the transmission site (Node-B)208 of FIG. 2.

The transmitter site 400 comprises an interface component 402 forreceiving media data from the RNC 206 in RAN 202, which may forward themedia data without processing. The interface component 402 forwards thereceived media data to first and second transmission control components404 and 406. The first component 404 is adapted for initiating a firsttransmission into a cell of the broadcast area 100 (see FIG. 1) servedby the transmitter. The second transmission control component 406 isadapted for initiating a second transmission into the cell. The secondtransmission may be adapted for reception in the region 108 of small ISDor the region 104 of large ISD. The initiation may comprise preparingthe media data for the transmissions (channel coding, associating themedia data to transmission frames, associating the frames to particulartime slots and/or frequency channels, determining the transmissionpower, etc.) and forwarding the processed data, i.e. the broadcast data,to the antenna 408 for transmission into the cell.

In other embodiments, the interface component may also comprisepreprocessing modules similar to the components 302, 322, 324 in FIGS.3A, 3B. The interface component segregating the media data stream forthe two transmission control components may also be located external tothe transmitter site, for example in an RNC or BSC of the RAN. Further,a transmitter site may comprise only one of the two transmission controlcomponents illustrated in FIG. 4. For example, the first transmissioncontrol component for preparing the first transmission may be locatedupstream in the RAN (or even the core network) and provide its dataoutput to multiple transmitter sites, as the first transmission isperformed into the entire broadcast area.

FIG. 5 schematically illustrates the functional components of anembodiment 500 of a user equipment for use with a mobile network, forexample the network providing the broadcast area 100 of FIG. 1 or thenetwork 202, 204 of FIG. 2.

The user equipment 500 comprises an antenna 502 and a receiver component504. The receiver component 504 may forward received media data tofurther components of the UE 500 (not shown), for example presentationcomponents for presenting the media data on a display associated withthe UE 500. The antenna 502 and/or the receiver 504 may comprise filtercomponents for filtering the received broadcast signal, which are alsoomitted in FIG. 5 for clarity.

The receiver stage 504 contains a first interface component 506 forreceiving a first broadcast transmission and a second interfacecomponent 508 for receiving a second broadcast transmission, bothtransmissions typically using different transmission resources. One ofthe transmissions is adapted for a region of small ISD of the broadcastarea, the other transmission is adapted for a region of large ISD of thebroadcast area.

Both interface components 506, 508 may comprise modules for recoveringmedia data from the received broadcast signal. The modules may extractbroadcast data from received transmission frames and may perform channeldecoding and functions for recovering a bit stream from broadcast datareceived in different time slots and/or frequency sub-channels. Afurther module 510 is provided for recombining a single media stream,for example in case a first transmission transmits a base layer ofmulti-layered media data and a second transmission transmits anenhancement layer of the media data. The module 510 may be omitted inthe receiver stage 504 in case a presentation component is able tocombine the base layer and the enhancement layer.

FIG. 6 is a flow chart which illustrates the steps of an embodiment 600of a method of controlling a wireless broadcast transmission of mediadata via multiple transmitter sites into a broadcast area with differentinter-site distances. The broadcast area comprises at least a region oflarge ISD and a region of small ISD. The method 600 may be implementedin one or more network nodes of a broadcast-enabled network, for examplethe RNC 206 or the transmitter sites 208, 210 of FIG. 2. In thefollowing, it is exemplarily assumed that the method 600 is performed inthe RNC-based broadcast control system 300 of FIG. 3A.

Execution of the method 600 is triggered in step 602 by a triggeringevent, for example the reception of media data intended for broadcasttransmission at the splitting component 302 of the broadcast controlsystem 300. The reception of the data triggers step 604, in which afirst transmission is initiated into the broadcast area, the firsttransmission being adapted for reception in a first one of the tworegions. The trigger event 602 further triggers step 606, in which asecond transmission into the second one of the regions is initiated, thesecond transmission being adapted for reception in the second region.The method stops in step 608, when for example the broadcast controlsystem 300 waits for further broadcast data to be transmitted.

It is to be understood that steps 604 and 606 may be performedsimultaneously. Alternatively, steps 604 and 606 may be performedsequentially, such that the radio resources of a particular transmittersite are utilized in a first time step for the first transmission and ina subsequent time step for the second transmission.

FIG. 7 is a flow chart which illustrates the steps of a furtherembodiment 700 of a method of controlling a wireless broadcasttransmission of media data via multiple transmitter sites into abroadcast area with different inter-site distances. Step 702 triggersexecution of steps 704, 706 and 708. For the embodiment 700 it isassumed that the media data comprise hierarchically layered data with abase layer and an enhancement layer. The media data may behierarchically coded at a media server providing the media data or inthe core network 204 (see FIG. 2).

The steps 704, 706 and 708 may for example be performed by thetransmission control components 304, 306 and 308, respectively, of thebroadcast control system 300 in FIG. 3A. The preprocessing (splitting)component 302 of the system 300 may act to split the multiple layermedia data stream into base layer and enhancement layer, and may forwardonly the base layer data stream to the control component 304 and onlythe enhancement layer data stream to the control components 306 and 308.

The step 704 is related to a transmission of the base layer and thesteps 706, 708 are related to a transmission of the enhancement layer.In step 704, a first transmission of the base layer is initiated intothe entire broadcast area. The first transmission is adapted forreception in the region of large ISD. In step 706, a secondtransmission, namely a transmission of the enhancement layer, isinitiated into the region of small ISD. The second transmission isadapted for reception in this region.

In step 708 it is determined if transmission resources for atransmission of the enhancement layer are available at one or moretransmitter sites of the region of large ISD. In case of availableresources, in step 710 (at least) a third transmission is initiated viathe one or more transmitter sites into the region of large ISD. Thethird transmission is adapted for reception of the enhancement layer inthe region of large ISD. Thus, the enhancement layer is available forreception not only in the region of small ISD, but also in the region oflarge ISD in case of available radio resources.

In particular embodiments, only for step 704 of the first transmissionof the base layer into the entire broadcast area an SFN transmissionmode may be used, whereas for the second and optionally thirdtransmission of the enhancement layer (steps 706, 708) each transmittersite uses a frequency different from the frequencies used by theneighbouring stations.

In other embodiments, a multimedia stream may comprise several baselayers and/or several enhancement layers. Generally the base layer orlayers provide a basic media presentation quality. The additionalreception of the one or more enhancement layer(s) increases thepresentation quality compared to the quality provided by the base layer.

The base layer is transmitted into the entire broadcast area and isadapted for reception in the region of large ISD in step 704. Morespecifically, this means that the transmission mode of the base layer interms of usage of time and/or frequency resources, transmission powerand channel coding provides for a broadcast signal that can besuccessfully decoded in the entire broadcast area, i.e. in the region ofsmall ISD and in the region of large ISD. This robust transmission modedoes not achieve the theoretically possible throughput in the region ofsmall ISD. However, in the embodiment 700 only the base layer istransmitted in this transmission mode. The second (third) transmissionof the enhancement layer is specifically adapted to the region of small(large) ISD, leading to a better overall resource usage.

For transmitting the enhancement layer in step 706 in the secondtransmission into the region of small ISD, particular radio resourcesare utilized such that the desired coverage in the region of small ISDis achieved. As an example, hierarchical modulation may be used, inwhich the I-Q modulation constellation of an enhancement layer issuperimposed to the constellation of the base layer, such that thelayers modulate the same time-frequency resource blocks. In otherembodiments, the enhancement layer and the base layer may be time and/orfrequency multiplexed on different resource blocks.

The third transmission of the enhancement layer into the region of largeISD uses more radio resources than the second transmission of theenhancement layer into the region of small ISD. As an example, in thesecond transmission the enhancement layer may be transmitted using 64QAMmodulation and in the third transmission the enhancement layer may betransmitted using 16QAM modulation (16QAM is a more robust modulationscheme than 64QAM). Using the same transmission resources, 16QAM has adata rate ⅔ the data rate of a 64 QAM modulated transmission. Thereforea 16QAM modulation used for the third transmission into the region oflarge ISD will require 50% more radio resources in the time and/orfrequency domain than the second transmission into the region of smallISD.

FIG. 8 is a flow chart illustrating the steps of another embodiment 800of a method of controlling a wireless broadcast transmission of mediadata via multiple transmitter sites into a broadcast area with differentinter-site distances. The method will exemplarily be illustrated withreference to the embodiment of a broadcast control system implemented inan RNC and Node-Bs in FIG. 3C.

The method is triggered in step 802, for example by the reception ofmedia data at the RNC 340. In step 804, in a bit stream associated withthe media data bits are indicated that may be omitted in a transmission.This step may comprise a common channel coding of the media data to bebroadcasted, which is performed by the encoding components 350, 358 andpuncturing performed in the components 352, 360. In step 806, a firsttransmission into the broadcast area is initiated. The firsttransmission is adapted for reception in the region of small ISD. Thebit stream excluding the omitted bits is transmitted into the broadcastarea. In a parallel step 808, a second transmission of the same encodedbroadcast signal is initiated into the region of large ISD. The secondtransmission is adapted for reception in the region of large ISD. Thebit stream including the omitted bits is transmitted.

The first and second transmissions are initiated by the first and secondtransmitter sites 342 and 344, respectively. The transmitter site 342may belong to the region of small ISD, whereas the site 344 belongs tothe region of large ISD. In step 810, the broadcast control systemsstops operation and waits for another triggering event.

The channel encoding in step 804 may comprise to apply for example achannel code with rate ⅓. Channel encoding might comprise convolutionalor turbo coding. The output stream of the channel encoder might then bepunctured, i.e. encoded bits may be suppressed from transmission bypuncturing. The punctured streams may be output as sub-streamsexcluding/including the punctured bits at the puncturing components 352and/or 352.

Accordingly, in step 806, only a sub-set of the encoded broadcast signalis transmitted, i.e. punctured bits are omitted from the firsttransmission into the broadcast area. This is possible, as with thecomparatively good reception conditions in the region of small ISD, notall of the encoded bits are required in order to decode a receivedbroadcast signal in good quality. The punctured bits are onlytransmitted in step 808 into the region of large ISD, as the puncturedbit stream (which can be received in the region of large ISD via thefirst transmission) is not sufficient to decode the media data with thedesired coverage in the region of large ISD.

Therefore, whereas the same media data are transmitted into the regionsof small and large ISD, the radio resources used for the transmissionsdiffer. The additional radio resources required in step 808 may compriseadditional symbols (e.g. OFDM symbols) or additional sub-carriers.Systematic bits (or bits of different importance for successfuldecoding) may not be omitted from transmission, as these bits arerequired for any successful decoding.

A receiver located in the region of small ISD only requires the firsttransmission. A receiver located in the region of large ISD may requirethe first and the second transmission. The receiver may combine the bitstransmitted via both transmissions prior to decoding.

In an alternative embodiment, redundancy is added to the broadcastsignal for the region of large ISD by transmitting multiplerepresentations or copies of the media data. The same channel codedinformation may thus be transmitted using multiple radio resourceblocks, defined by at least one of time intervals and frequencychannels. As an example, the encoded broadcast signal may be transmittedin multiple OFDM symbols, i.e. multiple copies in the time domain. Inthe alternative, the same information may be transmitted via multiplesets of OFDM sub-carriers (multiple copies in the frequency domain).

FIG. 9 is a flow chart illustrating a still further embodiment 900 of amethod of controlling a wireless broadcast transmission of media datavia multiple transmitter sites into a broadcast area with differentinter-site distances, wherein the broadcast area comprises at least aregion of large ISD and a region of small ISD. The method describes theoperation of a broadcast control system implemented in a transmittersite, for example in the transmitter site 400 of FIG. 4.

In step 902, the transmitter site is triggered, e.g., by the receptionof media data intended for wireless broadcast transmission. In step 904,a first transmission is initiated into a cell served by the transmittersite. The first transmission is adapted for reception In the region oflarge ISD. in the parallel step 906, a second transmission is initiatedinto the cell. The second transmission is adapted for reception in theregion of small ISD of the broadcast area. In step 908, the method 900ends and waits for a new triggering event.

As an example, the transmitter may be located anywhere in the broadcastarea and the first transmission may comprise the transmission of a baselayer and the second transmission may comprise the transmission of anenhanced layer of multi-layer media data (the location of thetransmitter in the region of large ISD or small ISD determines theparticular radio resources utilized). As another example, thetransmitter may be located in the region of large ISD and the secondtransmission may comprise the transmission of a broadcast signalutilizing radio resources, which are only sufficient for coverage in theregion of small ISD and nearby the transmitter sites in the region oflarge ISD. The first transmission utilizes additional radio resources toachieve complete coverage also in the region of large ISD.

FIG. 10 is a flow chart illustrating an embodiment 1000 of a method forreceiving a wireless broadcast transmission of media data via multipletransmitter sites into a broadcast area with different inter-sitedistances. Again, the broadcast area comprises at least a region oflarge ISD and a region of small ISD. The method 1000 is exemplarilydiscussed with reference to the embodiment 500 of a user equipment witha receiver component 504 in FIG. 5.

In step 1002, the receiver is triggered, for example, by the receptionof broadcast data via antenna 502. In step 1004 a first transmission isreceived from at least one transmitter site. The first transmission isadapted for reception in the region of large ISD. In a parallel step1006, a second transmission is received from at least one of thetransmission sites. The second transmission is adapted for reception inthe region of small ISD.

Several neighbouring transmitter sites may synchronously transmit thefirst and/or the second transmission. The receiver may thus receive thefirst and the second transmission from different sets of transmittersites. For example, in case the receiver is located in a border zonebetween the region of large ISD and the region of small ISD, thereceiver may receive a first transmission, which is transmitted from alltransmitters in the broadcast area, whereas a second transmission isonly transmitted by transmitter sites in the region of small ISD.

For all embodiments, it is to be noted that in addition to transmittingmedia data, also signalling data might be broadcasted into the broadcastarea to indicate the utilized radio resources for the first, second andpossibly third transmission. For example, an existing signalling channelaccording to a signalling framework of a mobile network may be used forthis purpose. As an example, the multicast control channel (MCCH) in aUMTS system may be used. The signalling data may also indicateinformation on the media data and its properties.

Only signalling data may be broadcasted into a particular region whichare required by the receivers located therein. For example, in case onlya base layer of layered media data is transmitted into a region of largeISD, signalling information regarding the second transmission into theregion of small ISD may be omitted from transmission into the region oflarge ISD. Part or all of the signalling data may be deduced by thereceiver (blind detection) at the cost of adding complexity to thereceiver.

The technique described above improves the spectral efficiency forsingle frequency networks in regions of small ISD, such that thebroadcast throughput may be increased in these regions without reducingthe coverage in the regions of large ISD in an unacceptable way. Thetechnique further flexibly improves broadcast quality in regions oflarge ISD by using additional transmission resources in case suchresources are available if these are, for example, temporarily notrequired for unicast transmissions.

In comparison to just increasing the transmission power for a particularresource block, adding additional radio resources in the time and/orfrequency domain distributes the power spectral density more equallyover the resource blocks in the time and frequency domain. Also, addingadditional resource blocks gains from time or frequency diversity, e.g.reduces the error rate caused by short-term or narrow-band noise andfast fading. Performing a common channel coding for the first and secondtransmissions and transmitting the punctured bits only in the secondtransmission achieves a gain also in interference limited cells.Further, this mechanism acts to increase the transmission bandwidth by afactor which is equal to the number of added resource blocks instead ofjust increasing the signal to noise ratio by that factor.

While the current invention has been described in relation to itspreferred embodiments, it is to be understood that this description isintended for illustrative, non-limiting purposes only. The inventionshall be limited only by the scope of the claims appended hereto.

1. A method of controlling a wireless broadcast transmission of mediadata via multiple transmitter sites into a broadcast area with differentinter-site distances, wherein the broadcast area comprises at least aregion of large inter-site distance and a region of small inter-sitedistance, and wherein the method comprises the steps of: initiating afirst transmission into the broadcast area, the first transmission beingadapted for reception in a first of the regions; and initiating a secondtransmission into a second of the regions, the second transmission beingadapted for reception in the second region.
 2. The method according toclaim 1, wherein the first transmission is adapted for reception in theregion of large inter-site distance and the second transmission isaccomplished into the region of small inter-site distance, the secondtransmission being adapted for reception in the region of smallinter-site distance.
 3. The method according to claim 2, wherein themedia data comprise hierarchically layered data with at least a baselayer and an enhancement layer, and wherein the step of initiating thefirst transmission comprises initiating a transmission of the base layerand the step of initiating the second transmission comprises initiatinga transmission of the enhancement layer.
 4. The method according toclaim 3, comprising the further step of determining if transmissionresources for a transmission of the enhancement layer are available atone or more transmitter sites of the region of large inter-sitedistance; and in case of available transmission resources, initiating athird transmission via the one or more transmitter sites into the regionof large inter-site distance, the third transmission being adapted forreception of the enhancement layer in the region of large inter-sitedistance.
 5. The method according to claim 4, wherein the secondtransmission comprises transmitting a single representation of the mediadata and the third transmission comprises transmitting multiplerepresentations of the media data.
 6. The method according to claim 4,comprising the further steps of transmitting a subset of the media dataof the enhancement layer via the second transmission, and transmittingthe media data of the enhancement layer via the third transmission. 7.The method according to claim 6, comprising the steps of indicating in abit stream associated with the media data of the enhancement layer bitsthat may be omitted in a transmission, transmitting the bit stream viathe second transmission excluding the omitted bits and transmitting thebit stream via the third transmission including the omitted bits.
 8. Themethod according to claim 4, wherein the transmitter sites of thebroadcast area perform the first transmission each utilizing one and thesame frequency and/or time resource and perform at least one of thesecond and third transmission(s) utilizing different frequency and/ortime resources.
 9. The method according to claim 1, wherein the firsttransmission is adapted for reception in the region of small inter-sitedistance and the second transmission is accomplished into the region oflarge inter-site distance, the second transmission being adapted forreception in the region of large inter-site distance.
 10. The methodaccording to claim 9, wherein one and the same broadcast signalrepresenting the media data is transmitted in the first transmission andin the second transmission, and the second transmission utilizes moretransmission resources than the first transmission.
 11. The methodaccording to claim 10, wherein the first transmission comprisestransmitting a single representation of the media data and the secondtransmission comprises transmitting multiple representations of themedia data.
 12. The method according to claim 10, comprising the furthersteps of: transmitting a subset of the media data via the firsttransmission, and transmitting the media data via the secondtransmission.
 13. The method according to claim 12, comprising the stepsof indicating in a bit stream associated with the media data bits thatmay be omitted in a transmission, transmitting the bit stream via thefirst transmission excluding the omitted bits and transmitting the bitstream via the second transmission including the omitted bits.
 14. Amethod of controlling a wireless broadcast transmission of media datavia multiple transmitter sites into a broadcast area with differentinter-site distances, wherein the broadcast area comprises at least aregion of large inter-site distance and a region of small inter-sitedistance, and wherein the method comprises the steps of: initiating afirst transmission into a cell served by a transmitter site, the firsttransmission being adapted for reception in the region of largeinter-site distance; and initiating a second transmission into the cell,the second transmission being adapted for reception in the region ofsmall inter-site distance.
 15. A method of receiving a wirelessbroadcast transmission of media data via multiple transmitter sites intoa broadcast area with different inter-site distances, wherein thebroadcast area comprises at least a region of large inter-site distanceand a region of small inter-site distance, and wherein the methodcomprises the steps of: receiving a first transmission from at least onetransmitter site, the first transmission being adapted for reception inthe region of large inter-site distance; and receiving a secondtransmission from at least one transmitter site, the second transmissionbeing adapted for reception in the region of small inter-site distance.16. The method according to claim 14, wherein the media data comprisehierarchically layered data with at least a base layer and anenhancement layer, and wherein the first transmission comprises atransmission of the base layer and the second transmission comprises atransmission of the enhancement layer.
 17. The method according to claim14, wherein one and the same broadcast signal representing the mediadata is transmitted in the first transmission and in the secondtransmission and the transmissions utilize different transmissionresources.
 18. (canceled)
 19. (canceled)
 20. A broadcast control systemfor controlling a wireless broadcast transmission of media data viamultiple transmitter sites into a broadcast area with differentinter-site distances, wherein the broadcast area comprises at least aregion of large inter-site distance and a region of small inter-sitedistance, and wherein the system comprises: at least one firsttransmission control component adapted for initiating a firsttransmission into the broadcast area, the first transmission beingadapted for reception in a first of the regions; and at least one secondtransmission control component adapted for initiating a secondtransmission into a second of the regions, the second transmission beingadapted for reception in the second of the regions.
 21. The broadcastcontrol system according to claim 20, wherein one of the at least onefirst transmission control components is adapted to initiate the firsttransmission, which is adapted for reception in the region of largeinter-site distance and one of the at least one second transmissioncontrol components is adapted to initiate the second transmission, whichis adapted for reception in the region of small inter-site distance. 22.The broadcast control system according to claim 20, wherein one of theat least one first transmission control components is adapted toinitiate the first transmission, which is adapted for reception in theregion of small inter-site distance and one of the at least one secondtransmission control components is adapted to initiate the secondtransmission which is adapted for reception in the region of largeinter-site distance.
 23. A transmitter for controlling a wirelessbroadcast transmission of media data via multiple transmitter sites intoa broadcast area with different inter-site distances, wherein thebroadcast area comprises at least a region of large inter-site distanceand a region of small inter-site distance, and wherein the transmittercomprises: a first transmission control component adapted for initiatinga first transmission into a cell of the broadcast area served by thetransmitter, the first transmission being adapted for reception in theregion of large inter-site distance; and a second transmission controlcomponent adapted for initiating a second transmission into the cell,the second transmission being adapted for reception in the region ofsmall inter-site distance.
 24. (canceled)
 25. A receiver stage forreceiving a wireless broadcast transmission of media data via multipletransmitter sites into a broadcast area with different inter-sitedistances, wherein the broadcast area comprises at least a region oflarge inter-site distance and a region of small inter-site distance, andwherein the receiver stage comprises: a first interface componentadapted for receiving a first transmission from at least one of thetransmitter sites, the first transmission being adapted for reception inthe region of large inter-site distance; and a second interfacecomponent adapted for receiving a second transmission from at least oneof the transmitter sites, the second transmission being adapted forreception in the region of small inter-site distance.
 26. The receiverstage of claim 25, wherein the receiver stage is part of user equipmentadapted for a mobile network.
 27. The method according to claim 15,wherein the media data comprise hierarchically layered data with atleast a base layer and an enhancement layer, and wherein the firsttransmission comprises a transmission of the base layer and the secondtransmission comprises a transmission of the enhancement layer.
 28. Themethod according to claim 15, wherein one and the same broadcast signalrepresenting the media data is transmitted in the first transmission andin the second transmission and the transmissions utilize differenttransmission resources.